COPR: Consistency-Oriented Pre-Ranking for Online Advertising
This addresses a specific bottleneck in large-scale advertising systems for platforms like Taobao, offering an incremental improvement over existing score alignment methods.
The paper tackles the inconsistency between pre-ranking and ranking models in online advertising cascading systems, which harms effectiveness, by proposing a consistency-oriented pre-ranking framework that improves click-through rate by up to 12.3% and revenue per mille by 5.6% when deployed.
Cascading architecture has been widely adopted in large-scale advertising systems to balance efficiency and effectiveness. In this architecture, the pre-ranking model is expected to be a lightweight approximation of the ranking model, which handles more candidates with strict latency requirements. Due to the gap in model capacity, the pre-ranking and ranking models usually generate inconsistent ranked results, thus hurting the overall system effectiveness. The paradigm of score alignment is proposed to regularize their raw scores to be consistent. However, it suffers from inevitable alignment errors and error amplification by bids when applied in online advertising. To this end, we introduce a consistency-oriented pre-ranking framework for online advertising, which employs a chunk-based sampling module and a plug-and-play rank alignment module to explicitly optimize consistency of ECPM-ranked results. A $ΔNDCG$-based weighting mechanism is adopted to better distinguish the importance of inter-chunk samples in optimization. Both online and offline experiments have validated the superiority of our framework. When deployed in Taobao display advertising system, it achieves an improvement of up to +12.3\% CTR and +5.6\% RPM.